/**
 * Copyright (c) 2010 by Kevin Bierhoff.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *    1. Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *    2. Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *    3. Neither the names of the authors nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ''AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package com.googlecode.syper.javasyp.checker;

import java.util.Map;

import com.googlecode.syper.javasyp.checker.ExpressionEncoder.Lookup;
import com.googlecode.syper.javasyp.formulae.Field;
import com.googlecode.syper.javasyp.formulae.Formula;
import com.googlecode.syper.javasyp.formulae.Local;
import com.googlecode.syper.javasyp.formulae.Name;
import com.googlecode.syper.javasyp.formulae.Pre;
import com.googlecode.syper.javasyp.formulae.RewritingVisitor;
import com.googlecode.syper.javasyp.formulae.Select;

/**
 * @author kevin
 * @since Jan 30, 2010
 *
 */
public class Substitution extends RewritingVisitor {

	private Map<String, Formula> subst;
	private Lookup lookup;
	private Lookup preLookup;
	private boolean usePre = false;

	public static Formula replace(Formula f, Map<String, Formula> subst, Lookup lookup) {
		Substitution s = new Substitution();
		s.subst = subst;
		s.lookup = lookup;
		return f.dispatch(s);
	}

	public static Formula replace(Formula f, Map<String, Formula> subst,
			Lookup lookup, Lookup preLookup) {
		Substitution s = new Substitution();
		s.subst = subst;
		s.lookup = lookup;
		s.preLookup = preLookup;
		return f.dispatch(s);
	}

	@Override
	public Formula visit(Local f) {
		Formula replace = subst.get(f.getId());
		if (replace == null)
			return f;
		return replace;
	}

	@Override
	public Formula visit(Field f) {
		Name obj = (Name) f.getObj().dispatch(this);
		Lookup l = usePre ? preLookup : lookup;
		return l.getField(obj, f.getBinding());
	}

	@Override
	public Formula visit(Pre f) {
		if (preLookup == null)
			throw new IllegalStateException("old not available: " + f);
		boolean oldUsePre = usePre;
		try {
			usePre = true;
			return f.getAged().dispatch(this);
		} finally {
			usePre = oldUsePre;
		}
	}

	@Override
	public Formula visit(Select f) {
		Formula array = f.getArray().dispatch(this);
		Formula index = f.getIndex().dispatch(this);
		// use array incarnation from appropriate lookup
		Lookup l = usePre ? preLookup : lookup;
		return l.getSelect(array, index, f.getType());
	}
}
